title: Chondroitin Sulfate in Solution: Effects of Mono- and Divalent Salts.
abstract: Chondroitin sulphate (CS) is a linear sulfated polysaccharide found in cartilage and other tissues in the body. Small angle neutron scattering (SANS) and dynamic light scattering (DLS) measurements are made on semi-dilute CS solutions to determine ion induced changes in the local order of the CS chains and in their dynamic properties. In salt-free CS solutions SANS detects the correlation peak due to local ordering between adjacent chains in which the characteristic interchain distance isd≈ 57 Å. In both monovalent and divalent salts (NaCl and CaCl2) aligned linear regions are distinguishable corresponding to distance scales ranging from the length of the monomer unit (8 Å) to about 1000 Å. With increasing calcium ion concentration, the scattering intensity increases. Even in the presence of 200 mM CaCl2, however, neither phase separation nor cross-linking occurs. DLS in the CS solutions reveals two characteristic relaxation modes, the fast mode corresponding to the thermal concentration fluctuations. The collective diffusion coefficientDdecreases with increasing calcium ion concentration and exhibits a power law function of the single variablec/J, wherecis the CS concentration andJis the ionic strength of the salt in the solution. This result implies that the effect of the sodium and calcium ions on the dynamic properties of CS solutions is fully accounted for by the ionic strength.
authors.affiliation: Section on Tissue Biophysics and Biomimetics, Program in Pediatric Imaging and Tissue Science, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 13 South Drive, Bethesda, MD 20892, USA.
authors.forename: Ferenc
authors.initials: F
authors.lastname: Horkay
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Basser
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Hecht
authors.forename: Erik
authors.initials: E
authors.lastname: Geissler
keywords: chondroitin sulfate; collective diffusion coefficient; polyelectrolyte solution; small angle neutron scattering dynamic light scattering